Photovoltaic silicone encapsulant and photovoltaic module

Abstract

A silicone composition for photovoltaic encapsulation is prepared by blending (A) an organopolysiloxane containing at least two silicon-bonded alkenyl groups per molecule, (B) an organohydrogenpolysiloxane containing at least two silicon-bonded hydrogen atoms per molecule, and (C) an addition reaction catalyst such that the composition when cured may have a water vapor permeability of 80-160 g/m 2 ·day at 40° C. and a thickness of 1 mm.

1 . In connection with a photovoltaic module comprising a photovoltaic cell having a front surface on which solar light is incident and a back surface, a front glass plate on the front surface, and a backsheet or back glass plate on the back surface,
 a silicone composition for encapsulating the photovoltaic cell comprising   (A) 100 parts by weight of an organ containing at least two silicon-bonded alkenyl groups per molecule, represented by the average compositional formula (1)
   R a R′ b SiO (4-a-b)/2    (1)
 
   
       wherein R is alkenyl, R′ is a substituted or unsubstituted monovalent hydrocarbon group of 1 to 10 carbon atoms free of aliphatic unsaturation, a and b are numbers in the range: 0<a≦2, 0<b<3, and 0<a+b≦3,
 (B) an organohydrogenpolysiloxane containing at least two silicon-bonded hydrogen atoms per molecule, in such an amount that a molar ratio of silicon-bonded hydrogen in component (B) to silicon-bonded alkenyl in component (A) may be in a range of 0.4/1 to 2.5/1, and 
 (C) a catalytic amount of an addition reaction catalyst, 
 the silicone composition, when cured, having a water vapor permeability of at least 80 g/m 2 ·day at 40° C. and a thickness of 1 mm. 
 
     
     
         2 . The composition of  claim 1  wherein the composition, when cured, has a modulus of elasticity of 0.1 to 5.0 MPa. 
     
     
         3 . A photovoltaic module comprising a photovoltaic cell having a front surface on which solar light is incident and a back surface, a front glass plate on the front surface, a backsheet or back glass plate on the back surface, and an encapsulant for encapsulating the cell, the encapsulant being the silicone composition of  claim 1 .